Causes Of Joint Pain In Dogs

Joint pain in dogs can be caused by either acute or chronic conditions. It can be caused by congenital defects, an injury to the joint, abnormal joint development, an infection, or an immune-related condition.

Joint pain can affect dogs of any age, although older dogs, like people, are particularly susceptible to arthritis. However, there are a number of conditions, like canine hip dysplasia, legg-perthes disease, and wandering lameness, that affect younger dogs. Most of these conditions are quite serious and require veterinary diagnosis and care. Of course, there are many acute, short term conditions, usually resulting from accidents, that can cause canine joint pain too.

This article discusses Joint sprains, tendon injuries, dislocated joints, stifle joint injuries, hip dysplasia, legg-perthes disease, and slipping kneecap.  The following article discusses other dog joint problems such as elbow dysplasia, osteochondrosis, wandering lameness, and Osteogenesis Imperfecta. For a full discussion on dog arthritis, see this article.

For information on dog joint pain relief, see this article.

Joint Sprains

Joint sprains are characterized by a temporary lameness, joint pain, and localized swelling around the joint. They affect the ligaments around the joint. Treatment requires the movements of the dog to be kept to a minimum by keeping him in a confined space. Apply cold packs during the first twenty four hours, then warm, moist (but not hot) packs for two to three days after this.

If there isn't an improvement within 24 hours, it's important to go to the vet as there may be other injuries.

Tendon Injuries

A dog's tendon, which connects the bone to the muscle, can become torn, over stretched, or completely ruptured. The severity of the injury will determine whether surgery is required to re-attach the muscle and tendon.

Symptoms include a painful swelling, pain when weight is placed on the leg, and lameness. If the tendon isn't completely ruptured, the treatment is similar to that which dogs with joint sprains receive.

Dislocated Joints

Dislocated joints are usually caused by an accident like falling from a significant height, or a car accident. Dogs are hit with sudden pain, and they cannot use the affected leg.

Joints can be partially dislocated also. In this case, the shortening of the leg that usually occurs with dislocated joints in dogs doesn't occur, and the joint may appear normal. Full and partial joint dislocations are an acute injury needing veterinary care.

Stifle Joint Injuries

The stifle is an important joint in the back (hind) legs of the dog, and said to be the equivalent of the human knee. There are a number of injuries that can affect this joint and cause canine joint pain. These are:

Torn Knee Ligament

There are a number of ligaments in a dog's 'knee' or stifle joint that can get torn, either due to over activity or a general weakening of condition due to age, weight and poor health. These ligaments are the anterior  (or cranial) cruciate ligament, the posterior or caudal cruciate ligament, and the medial and lateral collateral ligaments.

Injury to the  cranial cruciate ligament is one of the most common. It usually affects younger, active dogs. However, older dogs can have weakened ligaments that are over stretched and only partially torn. This general weakening can happen slowly, so that when the problem is precipitated, it is only a slight, seemingly normal movement - such as jumping off a bed - that does it.

If there is a sudden lameness in the back leg of your dog, it is most probably a torn cranial ligament. It is important to get veterinary care as soon as you notice a problem, as this type of injury can disappear after a few weeks, only to become exacerbated and reappear later. Rest might improve the injury, but the knee will be swollen, and arthritis can set in rapidly. And this sort of injury usually returns after exercise.

Torn Meniscus

Most dogs who experience a torn meniscus do so as a result of injuries to one or all of the cruciate ligaments. This is particularly true if the cruciate injury isn't treated. The cruciate ligaments provide stability to the stifle joints. Without a properly functioning cruciate, degenerative arthritis starts to develop, leading to permanent joint damage and chronic canine joint pain.

The meniscus, which are kidney-shaped cartilage, also play a role in keeping the stifle joint stable. It's important to really restrict exercise after cruciate injury and surgery in order to prevent arthritic changes.

Canine Hip Dysplasia

Canine hip dysplasia is a genetic condition that may or may not affect all dogs in the litter. Even though it is a condition usually associated with larger breed dogs, due to the problem of the increased weight on malfunctioning joints, smaller dogs can still be affected. They usually remain asymptomatic, however.

Canine hip dysplasia is a very common cause of arthritis, though the two are separate diseases. It comes about when the skeletal growth rate exceeds that of the growth rate of the muscles, ligaments, tendons, and other connective tissue that act to support and stabilize healthy joints. In dogs with hip dysplasia, the joint becomes progressively more unstable and loose as the weight on the joint increases, and the connective tissue is unable to support that weight. Wear and tear on the joint increases as the disease progresses and the joint degenerates.

There are three stages of canine hip dysplasia - mild, moderate, and severe. In mild dysplasia, there are no arthritic changes. However, arthritis starts to appear in the moderate stage, and progresses in the severe stage. Unfortunately, once arthritis is present, hip dysplasia cannot be reversed.

The disease can start as early as 4 to 12 months in genetically predisposed puppies. An x-ray, for which he may need to be sedated, is how the diagnosis of hip dysplasia is confirmed.

Legg-Perthes Disease

Legg-Perthes Disease is a disorder that affects puppies, especially toy breeds like the West Highland White and Yorkshire Terriers. The blood supply to the femoral head (the 'ball' in the 'socket' of the hip joint) is interrupted, though we still don't really know why. This causes the death of bone cells in the femur. Puppies are affected between 4 and 11 months of age.

Once the damage has occurred within the bone of the dog, his normal weight on his legs will cause the dead bone to collapse. This can result in a fracture to the cartilage, and secondary arthritis as the hip joint is gradually destroyed. Dogs with Legg-Perthes disease become lame, unable to hold their weight, with a loss of range of motion in the affected joint. There is also muscle wasting, and his leg will appear shorter.

Legg-Perthes is diagnosed with an x-ray, and surgery is required to remove the dead bone. 

Slipping Kneecap

Slipping kneecap is known as 'luxating patella'. It occurs when the small bone that protects the front of the stifle joint, called the patella, slips out of the groove on the bone where it usually is kept by ligaments. This problem occurs when the dog's knee bends, and happens because the groove is too shallow. Whether it slips out to the right or the left determines whether it is medial luxation (slips out to the inside of the knee joint), or lateral luxation (slips to the outside).

The luxating patella is a genetic issue that doesn't really occur as a result of some trauma. It affects both small and large breed dogs, although small breed dogs don't tend to get lateral luxation. This noticeably affects large and giant breeds when they are puppies, at about 6 months old. It is not as common as medial luxation, which does affect toy and miniature breeds as well as large breeds.

Lateral luxation tends to affect both legs, whereas medial luxation generally affects only one.

References: Griffin & Carlson, Dog Owner's Home Veterninary Handbook